Photoelectric controlled oscillator device



Feb, 23, 1943. F. H. SHEPARD, JR

PHOTOELECTRIC CONTROLLED OSCILLATOR DEVICE Filed Nov. '7, 1939 Rm, .w mR m m m T A H m C M m J n Y wEEB B m QN/ 1| w n xwmm dun LEG Ill. LL-EEQ F4463 mkmxmm mm lllll IL L L m 566% @T d I I I I I I I l l I I I II l l I l I I l Ill u x o E M23 mmkom the same power line at convenientPatented Feb. 23, 1943 rnoronancrnrc coN'rRoLLnn osomaaron DEVICEFrancis H. Shepard, Jr Merchantville, N. (5., assignor to RadioCorporation at America, a corporation of Eel-aware Application November7, 1939, Serial No. 303,191

4 Ciaims. (Cl. 177-352) My present invention relates to oscillatorscontrolled by photo-electric devices, and more particularly to alarmsystems utilizing light-controlled oscillator circuits for generating asignal wave capable of being detected it a point remote from theoscillator.

One of the main objects of my invention is to provide an alarm system inwhich capacity and photo-electric units may be plugged into the nearestalternatin current outlets of a. power line, and made to place a signalwave on the power -line on the approach of an intruder whereby a largeresidence, store, warehouse or ofllce building can be protected withoutthe necessity of costly installation wiring costs.

Another important-object of this invention is to provide a signallingsystem wherein a lightcontrolled oscillator is connected to a power linefor energization, and the power line functioning as a wave transmissionline as well; one or more signal wave indicator-devices being luggedinto places remote from'the oscillator.

Another object of my, present-invention is to provide burglar alarmsystemswhich dispense with the need forexpe'nsive wiring installations,and wherein the signalling device is a photo-electrically controlledoscillator which is plugged into thee'x'isting power line; a simpleone-tube relay alarm circuit being plugged into the power line atanydesirable remote point to indicate the si naljoscillations transmittedover the power line. Still other objects of this invention are toimprove generally. the simplicity and efflciency of burglar alarmsystems, and'moreespecially to provide an alarm system which is not onlydur-- able and reliable in operation, but is'economical to manufactureand install.

The novel features which I believe to be characteris'tic of my inventionare set forth in particularity in the appended claims; the inventionitselLhowever, as, to both its organization and m i e bd of operationwill best be understood by reference to'the following description takenin connection with the drawing in which I have indicateddiagrammatically a circuit organization whereby my invention may becarried into eflect.

Referring now to the accompanying drawing, I there. is shown a powerline I ;-which is to be understood as transmitting 60 cycle currentthrough a structure such as; a large residence, a store, warehouse or anomce building; I Assume that the room, or area, where-socket 2 islocatedis to be protected against intruders. There is. then, plugged in o t e;wi ket. t e p on s a plus 8.

which functions to provide the means for feeding energizing current tothe tubes of the oscillator, and which also acts to transmit thesignalling oscillations to the power line i for transmission to one ormore remote points. The light-controlled oscillator comprises anoscillator tube 4 which may be of the 25A6G type.

This type of tube may be a .pentode employing an indirectly heatedcathode. The tube t includes the anode 5, cathode 6, control grid l,intermediate grid 8 and suppressor grid 9. Both the heater filament land cathode s are tied to the lead I: which is connected to one terminalof the plug 3.

The plate is connected to the other terminal of plug 3 through a pathincluding coil l2 and lead Hi. The grid 2 is tied to the lead It), whilegrid 9 is tied to the cathode B. The coil l4 connects cathode dto thecontrol grid l through blocking condenser I5. The adjustable condenserl6 connects the coils It and I2 in series, and

' acts to resonate the oscillator to the operating frequency desired forthe signal waves to be transmitted over power line i. Coils l2 and M arestrongly coupled by the condenser l6. The tube ll, which may be apentode of the 6J7 type, acts as an amplifier for the output voltage ofand hence is used to biasthe grid 1 of oscillator sistor 32. The latteris included in series with the photo-electric tube l8. The latter may bea phototube of th 922 type, for example. Tubes I1 and l are connectedback to back; the potential of plate 21 is negative with respect to lineH 4. The anode IQ of the phototube is connected to lead II. The cathodeis connected to a movable tap 2!, the latter being adjustable alongcathode resistor 22, through resistor 23 and condenser 24 arranged inseries. Condenser 24 increases the sensitivity of the device, andeliminates instability due to contact potential variations. The cathodeend of resistor 23 is connectvecl by lead 25 to the control grid 26 ofamplifier ll. The plate 21 is connected through resistor 28 to lead I l,condenser 29 by-passing the resistor. The anode end of resistor 28 isconnected by resistor 30 to grid 1. The screen grid of tube I1 isconnected by slider 3! to any desired point on rethe heater elements33=and to. The cathode 34 is tied to filament 33, and the latter isconnected to lead IS. The condenser 35 by-passes that portion ofresistor 32 between tap 3| and cathode 34, whilecondenser 36 by-passesthe cathode resistor 22.

There is provided a light source 40 which projects a. beam of light itupon the cathode 20 of -photo electric tube 98. The tap 2| is adiustedalong resistor 22 towards the bottom thereof with light on the cathode20. The tap 2| is now moved towards the top thereof past the point atwhich the oscillator l is prevented from oscillating. If. now, anyobstacle is placed between the light source 40 and the phototube l 8which cuts of! the light beam 4!, oscillations will again commence.These oscillations, or waves, are impressed upon the 'power line i andtransmitted over the power line. At a remote room, or area, thereislocated any desired type of detector 50 followed by arelay device 5 I,the latter operating any desired indicator 52. It will, therefore, beunderstood that the rectangle designated "represents a remote locationat which point an indicator or alarm device is connected to the powerline to respond to the oscillations transmitted over the line. .The

detector may consist of a single tube connectedto function as the usualdetector of unmodulated carrier waves, andthe relay and indicator devicecan be of any well known construction. The incondensers II and 88 asshown, and by shielding the grid wires of tube ll, a.back-lash eifect iseliminated. This latter eifect is due to a radio frequency feedback tothe tube II. With "backlash eifect eliminated, and a fairly stable powerline, the circuit will operate satisfactorily for small light changes.If the line has large voltage variations it is wise to make the circuitinsensitive to small light changes. This is normally easily provided forin relay operation. If high light intensities are'used (more than 0.llumen) the cathode of tube II and the upper end of resistor 22 should bereturned to a higher point on resistor 32. The indicator 2 can be in theform of a light, floodlight, bell. a siren, an annunciator, or any otherwell known device.

The following constants are given for the oscillator network by way ofillustration, and it is to be clearly understood that these figures arein no way restrictive:

While l have indicated and described a system for carrying my 'inventioninto effect, it will be pass over the power line. It is to be understood7 that the frequencies may be in the :audio, or radio ranges. Ingeneral, when thebeam of light ll is interrupted by an intruder orobstruction the alternating current-bias qn the grid 26 of the amplifiertube l'l cuts off the plate current of the tube. This causes the voltagedrop across the plate load resistor 28 to decrease thereby removing thenegative voltage from the grid I of the oscillator tube. Such removal ofnegative voltage allows the oscillator tocommence oscillating, and theoscillator voltage is impressed upon the power line throughtheoscilappaarent to one skilled in the art that my inlator tank circuitwhich is series resonant with l negative part of the alternating currentcycle the condenser tends to charge up by drawing grid current to thepeak voltage betweencathode 24 and the setting of tap 2|. On the activepositive half-cycle the voltage on the grid is equal to the voltageacross the condenser due to that condenser charge plus the alternatingcurrent voltage applied through the condenser organization shown anddescribed, but that many modifications may be made without departingfromthe scope of my invention, as set forth in the appended claims.

What I claim is: V 1. In combination with an alternating current powerline, an oscillator network, light-responsive means for normallypreventing oscillation production by said network, means forconnecting'said network to said power line for energisation of thenetwork with alternating current from said line, means for coupling saidnetwork in oscillation energy transfer relation to said line whereby theline-functions as .the transmission medium for the oscillations, meansconnected to said power line at a point remote from said network forindicating oscillations transmitted over said line iromsaid network,said light-responsive means including a light source,

a phototube having light from said source impressed thereon, and a tubeenergized bysaid power line and-responsive to current ilow from resistor22 minus the drop in the resistor 23 determined by the amount of lighton phototube It. Thus, when there is plenty of light on the phototubethe grid 26 is eifectively above cut-oil, and the tube 11 draws platecurrent thereby charging the condenser 29 negative. This negativevoltage cuts oil the oscillator tube through the path including resistor3!, and thus no oscillation pulses are put'onthe power line.

through said phototube for rendering's'aid oscillator networkinoperative.

2. In'combination with an alternating "current power line, an oscillatornetwork, light-responsive means for normally; preventing oscillationproduction by said network, means for connecting said network to saidpower line for energiza- 'tion of the network from .said line, means forcoupling said network in oscillation energy 1 transfer relation to saidline whereby the line functions as the transmission medium for theoscillations, means connected to said power line at a point remote fromsaid network for indicating oscillationstransmitted over said line fromsaid network; said oscillator network ineluding a tube having-input andoutput electrodes coupled to provide said oscillations', a second tubehaving an output circuit arranged to control the potential differencebetween oscillator tube input electrodes, said energization meansapplying alternating current from said line to both said tubes toenergize them, and said light-responsive means including an element forcontrolling the conductivity of said second tube. v

3. In combination with an alternating current power line, an oscillatornetwork, light-responsive means for normally preventing oscillationproduction by said network, means for connecting said network to saidpower line for energization of the network with alternating current fromthe iine, means for applying said oscillations to said line whereby thelatter acts as a transmission line for the oscillations, means connectedto 'said power line at a point remote from said network for indicatingoscillations transmitted over said line from said network, saidoscillator network including a tube having input and output electrodescoupled to provide oscillations of a predetermined frequency, a sec. ondtube having an output resistive impedance arranged in its space currentpath, means to apply voltage developed across said impedance to saidoscillator tube input electrodes in a cutoff sense, said second tubeincluding a control electrode, said light-responsive means including aphoto-electric tube having a control connection to said controlelectrode such that space current flows normally through said resistiveimpedance.

4.121 combination with an alternating current power line, an oscillatornetwork, lightresponsive means for normally preventing oscillationproduction by said network, means for connecting said network to saidpower line for energization of the network with alternating current fromthe line, means for applying said oscillations to said line whereby thelatter acts as a transmission line for the oscillations, means connectedto said power line at a point remote from said network for indicatingoscillations transmitted over said line from said network, saidoscillator network including a tube having input and output electrodescoupled to provide oscillations of a predetermined frequency, a secondtube having an output resistive impedance arranged in its spacecurrent'path, means to apply voltage developed across said impedance tosaid oscillator tube input electrodes in a cut-off sense, said secondtube including a control electrode, said light-responsive-meansincluding a photo-electric tube having a control connection to saidcontrol electrode such that space current flows normally through saidresistive impedance, and connections from said line to the electrodes ofeach of said oscillator tube, second tube and photo-electric tubethereby to energize them with said alternating current.

FRANCIS H. SHEPARD, JR.

